Rabbits have peg teeth behind their incisor teeth. We normally never see them (of course). I’m thinking the weird thin one could be a peg teeth. The incisor teeth could grow out again. They often do unless the damage is deep -rabbits’ teeth grow all the rabbit’s life.

Rabbit teeth grow fast, but they can grow out crooked and having lost an incisor can mean that the bun uses its molar teeth differently, and that can cause molar spurs. There’s not a lot you can do to prevent that except try and make sure your bunny eats plenty of hay.

Rabbits can live without their incisors -some buns have to have them pulled for reasons of malocclusion. The rabbit mostly uses the incisors to pull food into its mouth -the actually chewing is done with the molars. As a rule a rabbit soon learns to eat without incisors, but you should of course keep an eye and you can feed her pellet mash in case she seems like she’s not eating enough.